Refactor HistoryDataStore into DictionaryDataStore+HistoryDataStore.
Separate out the part that writes the dictionary to a file store into a separate class, DictionaryDataStore.

R=xiyuan@chromium.org
BUG=None.
TEST=Unit tests pass, search cross-session functionality works correctly.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=228857

Review URL: https://codereview.chromium.org/26179007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230095 0039d316-1c4b-4281-b951-d872f2087c98
Refactoring of the NetworkPortalDetector. Observers of the
NetworkPortalDetector explicitly unsubscribe themselves during
destruction.

BUG=302812
TEST=unit_tests:NetworkPortalDetector*

Review URL: https://codereview.chromium.org/26657004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230096 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230095
SVN changes up to revision 230096
Revert the suppression for a false positive in localtime_r (fixed by a recent Clang roll)

BUG=304178
TBR=timurrrr@chromium.org

Review URL: https://codereview.chromium.org/34673003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230097 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230097